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POA better way to validate URL in C# than try-catch?
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  1. POA better way to validate URL in C# than try-catch?
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    copied!<p>I'm building an application to retrieve an image from internet. Even though it works fine, it is slow (on wrong given URL) when using try-catch statements in the application. </p> <p>(1) Is this the best way to verify URL and handle wrong input - or should I use Regex (or some other method) instead?</p> <p>(2) Why does the application try to find images locally if I don't specify http:// in the textBox?</p> <pre><code>private void btnGetImage_Click(object sender, EventArgs e) { String url = tbxImageURL.Text; byte[] imageData = new byte[1]; using (WebClient client = new WebClient()) { try { imageData = client.DownloadData(url); using (MemoryStream ms = new MemoryStream(imageData)) { try { Image image = Image.FromStream(ms); pbxUrlImage.Image = image; } catch (ArgumentException) { MessageBox.Show("Specified image URL had no match", "Image Not Found", MessageBoxButtons.OK, MessageBoxIcon.Error); } } } catch (ArgumentException) { MessageBox.Show("Image URL can not be an empty string", "Empty Field", MessageBoxButtons.OK, MessageBoxIcon.Information); } catch (WebException) { MessageBox.Show("Image URL is invalid.\nStart with http:// " + "and end with\na proper image extension", "Not a valid URL", MessageBoxButtons.OK, MessageBoxIcon.Information); } } // end of outer using statement } // end of btnGetImage_Click </code></pre> <p><strong>EDIT:</strong> I tried the suggested solution by Panagiotis Kanavos (thank you for your effort!), but it only gets caught in the if-else statement if the user enters <code>http://</code> and nothing more. Changing to UriKind.Absolute catches empty strings as well! Getting closer :) The code as of now:</p> <pre><code>private void btnGetImage_Click(object sender, EventArgs e) { String url = tbxImageURL.Text; byte[] imageData = new byte[1]; Uri myUri; // changed to UriKind.Absolute to catch empty string if (Uri.TryCreate(url, UriKind.Absolute, out myUri)) { using (WebClient client = new WebClient()) { try { imageData = client.DownloadData(myUri); using (MemoryStream ms = new MemoryStream(imageData)) { imageData = client.DownloadData(myUri); Image image = Image.FromStream(ms); pbxUrlImage.Image = image; } } catch (ArgumentException) { MessageBox.Show("Specified image URL had no match", "Image Not Found", MessageBoxButtons.OK, MessageBoxIcon.Error); } catch (WebException) { MessageBox.Show("Image URL is invalid.\nStart with http:// " + "and end with\na proper image extension", "Not a valid URL", MessageBoxButtons.OK, MessageBoxIcon.Information); } } } else { MessageBox.Show("The Image Uri is invalid.\nStart with http:// " + "and end with\na proper image extension", "Uri was not created", MessageBoxButtons.OK, MessageBoxIcon.Information); } </code></pre> <p>I must be doing something wrong here. :(</p>
 

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